400 error

How can I fix this issue the correct way? As it seems to appear after a while at random times... the only way to fix is to go from 2.0.x to 2.2.x or vice versa.

Error below:

Code:

Bad Request
Your browser sent a request that this server could not understand.
Reason: You're speaking plain HTTP to an SSL-enabled server port.
Instead use the HTTPS scheme to access this URL, please.
Hint: https://mysite:80/
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.